The overall objective of this proposal is to elucidate the nature and inflammatory role of immune complexes (IC) trapped in joint collagenous tissues (JCT) of patients with rheumatoid arthritis (RA) and of an antigen-induced rabbit model of chronic arthritis resembling RA. The interaction of polymorphonuclear leukocytes (PMN) and macrophages with the IC trapped in JCT will be studied in vitro both in RA and in the animal model. A model of pannus formation, which is one of the most important factors leading to joint destruction in RA, will be established by the use of organ culture techniques. The nature of the antibody specificity of the IC trapped in rheumatoid JCT will be studied. The possible rheumatoid factor and anti-collagen antibody activity will be investigated. The availability of collagen antigenic sites in normal and inflamed joint tissues will be examined. The interactions and mode of trapping of these complexes within the tissues will be elucidated by studying the possible role of Clq and of pre-existing free antibody in the extravascular compartment. The importance of pre-existing free antibody in the trapping of IC within renal glomerulus will also be investigated.